US5844368A

US5844368A - Driving system for driving luminous elements

Info

Publication number: US5844368A
Application number: US08/806,457
Authority: US
Inventors: Yoshiyuki Okuda; Shinichi Ishizuka
Original assignee: Pioneer Electronic Corp
Current assignee: Pioneer Corp
Priority date: 1996-02-26
Filing date: 1997-02-26
Publication date: 1998-12-01
Anticipated expiration: 2017-02-26
Also published as: JP3507239B2; JPH09232074A

Abstract

A driving system and driving unit for driving luminous elements has a fast build-up speed from the application of voltage to the point of light emission, thereby allowing fast scanning, as well as the capacity for miniaturization of driving sources. The driving system for driving luminous elements includes a plurality of intersecting anode and cathode lines arranged in a matrix, the anode lines being one of scan lines and drive lines, and the cathode lines being the other of scan lines and drive lines; a plurality of luminous elements, each of the luminous elements being coupled to one of the scan lines and one of the drive lines at a point where the scan and drive lines intersect; and control circuitry for causing at least one of the luminous elements to emit light by executing scanning of at least one of the scan lines and, during a predetermined period of the scanning, by coupling a driving source to at least one of the drive lines in synchronism with the scanning, the control circuitry resetting the scan lines before switching to a subsequent scan line by coupling each of the scan lines to a same reset voltage potential.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a driving system for causing luminous elements, such as organic EL (electroluminescense) elements, to emit light.

2. Description of Related Art

FIG. 13 shows a conventional driving system for driving luminous elements. The driving system shown in FIG. 13 is known as a simple matrix driving system in which anode lines A₁ through A_m and cathode lines B₁ through B_n are disposed in a matrix (grid). In the driving system of FIG. 13, luminous elements E₁,1 through E_m,n are connected at each intersection of the anode lines and cathode lines. The driving system causes the luminous element at an arbitrary intersection to emit light by selecting and scanning one of the anode lines and the cathode lines sequentially at fixed time intervals and by driving the other of the anode and cathode lines by current sources 52₁ through 52_m, i.e., driving sources, in synchronism with the scan.

Thus, there are two systems for driving luminous elements by means of the driving sources: (1) a system of scanning the cathode lines and driving the anode lines and (2) a system of scanning the anode lines and driving the cathode lines. FIG. 13 shows the former case of scanning the cathode lines and driving the anode lines.

In FIG. 13, a cathode line scanning circuit 51 is connected to the cathode lines B₁ through B_n and an anode line driving circuit 52 comprising the current sources 52₁ through 52_m is connected to the anode lines A₁ through A_m. The cathode line scanning circuit 51 applies a ground potential (0 V) sequentially to the cathode lines B₁ through B_n by scanning these lines while switching switches 53₁ through 53_n to the side of a ground terminal at fixed time intervals. The anode line driving circuit 52 connects the current sources 52₁ through 52_m with the anode lines A₁ through A_m by controlling ON/OFF of switches 54₁ through 54_m in synchronism with the scanning of the switches of the cathode line scanning circuit 51 to supply driving current to the luminous element at the desired intersection.

When the luminous elements E₂,1 and E₃,1 are to emit light, for example, the switches 54₂ and 54₃ of the anode line driving circuit 52 are switched to the side of the current sources to connect the anode lines A₂ and A₃ with the

current sources

52₂ and 52₃. At the same time the switch 53₁ of the cathode line scanning circuit 51 is switched to the ground side so that ground potential is applied to the first anode line B₁, as shown in FIG. 13. The luminous elements are controlled so that the luminous element at an arbitrary position emits light and so that each luminous element appears to emit light concurrently by quickly repeating such scan and drive.

A reverse bias voltage V_cc, which is equal to the source voltage, is applied to each of the cathode lines B₂ through B_n. The reverse bias voltage V_oc is not applied to the cathode line B₁ being scanned in order to prevent erroneous emission. It should be noted that although the current sources 52₁ through 52_m are used as the driving sources in FIG. 13, the same effect may be realized also by using voltage sources.

Each of the luminous elements E₁,1 through E_m,n connected at each intersection may be represented by a luminous element E having a diode characteristic and a parasitic capacitor C connected in parallel, as shown by the equivalent circuit in FIG. 14. However, the prior art driving system described above has had problems due to the parasitic capacitor C within the equivalent circuit. The problems are described as the following.

FIGS. 15A and 15B show each of the luminous elements E₁,1 through E₁,n using only the parasitic capacitors C described above by excerpting the part of the luminous elements E₁,1 through E₁,n connected to the anode line A₁ in FIG. 13. When the cathode line B₁ is scanned and the anode line A₁ is not driven, the parasitic capacitors C₁,2 through C₁,n of the other luminous elements E₁,2 through E₁,n (except the parasitic capacitor C₁,1 of the luminous element E₁,1 connected to the cathode line B₁ currently being scanned), are charged by the reverse bias voltage Vcc applied to each of the cathode lines B₁ through B_n, in the direction as shown in FIG. 15A.

Next, when the scanning position is shifted from the cathode line B₁ to the next cathode line B₂ and the anode line A₁ is driven in order to cause the luminous element E₁,2 to emit light, for example, the state of the circuit is shown in FIG. 15B. Thus, not only is the parasitic capacitor C₁,2 of the luminous element E₁,2, which emits light changed, but the parasitic capacitors C₁,1 and C₁,3 through C₁,n of the luminous elements E₁,1 and E₁,3 through E₁,n connected to the other cathode lines B₁ and B₃ through B_n, also are charged because currents flow into the capacitors in the direction as indicated by arrows.

In general, luminous elements cannot emit light normally unless a voltage between both ends thereof builds up to a level which exceeds a specified value. In the prior art driving system discussed above, not only is the parasitic capacitor C₁,2 changed when E₁,2 is to emit light, but the parasitic capacitors C₁,3 through C₁,n of the other luminous elements E₁,3 through E₁,n are charged as well. As a result, the end-to-end voltage of the luminous element E₁,2 connected to the cathode line B₂ cannot build up above the specified value until the charging of all of these parasitic capacitors of the luminous elements is completed.

Accordingly, the prior art driving system has had a problem in that the build up speed until emission is slow. Also no fast scan can be attained due to the parasitic capacitors described above. Further, because the parasitic capacitors of all of the luminous elements connected to the anode line have to be charged, a current capacity of the driving source for driving the luminous elements connected to each anode line must be large, thus leaving room for consideration from the aspect of miniaturization of the circuit.

The more the number of the luminous elements, the more significant the aforementioned problem becomes. When organic ELs are used as the luminous elements, this problem becomes remarkable because the organic EL has a large parasitic capacitor C surface-emission.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a driving system for driving luminous elements that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

It is an object of the present invention to solve the aforementioned problems by providing a luminous element driving system and a driving unit whose build up speed from the start of supply of driving current to emission is fast, thus enabling fast scanning. Another object is to provide a luminous element driving system and driving unit which allow the driving source to be miniaturized.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the driving system for driving luminous elements includes a plurality of intersecting anode and cathode lines arranged in a matrix, the anode lines being one of scan lines and drive lines, and the cathode lines being the other of scan lines and drive lines; a plurality of luminous elements, each of the luminous elements being coupled to one of the scan lines and one of the drive lines at a point where the scan and drive lines intersect; and control circuitry for causing at least one of the luminous elements to emit light by executing scanning of at least one of the scan lines and, during a predetermined period of the scanning, by coupling a driving source to at least one of the drive lines in synchronism with the scanning, the control circuitry resetting the scan lines before switching to a subsequent scan line by coupling each of the scan lines to a same reset voltage potential.

In the driving system, the potential of the reset voltage source is preferably a ground potential. Nonetheless, the potential of the reset voltage source may be also a supply potential. Moreover, in the driving system of the present invention, all of the driving sources on the drive side may be eliminated if so desired.

By the construction described above, when the scanning position is switched to the next scan line after resetting all the scan lines, the parasitic capacitor of the luminous element that is to emit light is charged by the driving source via the drive line and by the reverse bias voltage of the scan lines at the same time through the parasitic capacitors of the other luminous elements which are not emitting light. Therefore, because an end-to-end voltage of the luminous element that is to emit light builds up to a voltage which allows the instant emission of light, the luminous element can emit light instantly.

Further, even if the driving sources on the drive line side are eliminated, the parasitic capacitor of the luminous element that is to emit light is charged by the reverse bias voltage of the scan line through the parasitic capacitors of the other luminous elements which are not emitting light and, as a result, will emit light for a short time. Accordingly, the lighting of the luminous elements may be controlled just as if such elements emit light continuously, even if the driving sources on the drive line side are eliminated by scanning with a period shorter than the emission time.

The above and other features and advantages of the present invention will become more apparent in the following description and the accompanying drawings in which like numerals refer to like parts.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate principles of the invention. In the drawings:

FIG. 1 illustrates a first step of a first driving system of the present invention;

FIG. 2 illustrates a second step of the first driving system of the present invention;

FIG. 3 illustrates a third step of the first driving system of the present invention;

FIG. 4 illustrates a fourth step of the first driving system of the present invention;

FIG. 5 illustrates a first step of a second driving system of the present invention;

FIG. 6 illustrates a second step of the second driving system of the present invention;

FIG. 7 illustrates a third step of the second driving system of the present invention;

FIG. 8 illustrates a fourth step of the second driving system of the present invention;

FIG. 9 illustrates a first step of a third driving system of the present invention;

FIG. 10 illustrates a second step of the third driving system of the present invention;

FIG. 10 illustrates a third step of the third driving system of the present invention;

FIG. 11 illustrates a third step of the third driving system of the present invention;

FIG. 12 illustrates a fourth step of the third driving system of the present invention;

FIG. 13 illustrates a prior art driving system;

FIG. 14 illustrates an equivalent circuit of a luminous element; and

FIGS. 15A and 15B illustrate charging/discharging states in shifting scans in the prior art driving system.

DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

FIGS. 1 through 4 show a first driving system of the present invention. This first driving system corresponds to a case in which all cathode lines and all anode lines are reset by dropping their voltage to a ground potential (0 V) once in a shifting scan to the next cathode line.

In FIGS. 1 through 4, the system comprises anode lines A₁ through A₂₅₆, cathode lines B₁ through B₆₄, luminous elements E₁,1 through E₂₅₆,64, a cathode line scanning circuit l, an anode line driving circuit 2, an anode line resetting circuit 3, and an emission control circuit 4. The cathode line scanning circuit 1 comprises scanning switches 5₁ through 5₆₄ for sequentially scanning each of the cathode lines B₁ through B₆₄. One terminal of each of the scanning switches 5₁ through 5₆₄ is connected to a reverse bias voltage source whose voltage is equal to the source voltage V_cc (e.g., 10 V) and the other terminal is connected to the ground voltage (0 V).

The anode line driving circuit 2 comprises current sources 2₁ through 2₂₅₆, i.e., driving sources, and driving switches 6₁ through 6₂₅₆ for selecting each of the anode lines A₁ through A₂₅₆. The anode line driving circuit 2 connects the current sources 2₁ through 2₂₅₆ to drive the luminous elements at a pertinent anode line by turning on an arbitrary driving switch.

The anode line resetting circuit 3 comprises shunt switches 7₁ through 7₂₅₆ for resetting the anode lines A₁ through A₂₅₆ to the ground potential (0 V).

It is noted that ON/OFF control of scanning switches 5₁ through 5₆₄, driving switches 6₁ through 6₂₅₆ and shunt switches 7₁ through 7₂₅₆, is controlled by the emission control circuit 4.

The operations for emitting light by means of the first driving system will be explained with reference to FIGS. 1 through 4. The operations described below will be explained by referring to an example when luminous elements E₁,1 and E₁,2 are caused to emit light by scanning the cathode line B₁ and, then, the luminous elements E₂,2 and E₃,2, are caused to emit light by shifting the scan to the cathode line B₂. Further, in order to facilitate this description, the luminous elements emitting light are indicated by the diode symbol and the other luminous elements that are not emitting light are indicated by the capacitor symbol. The reverse bias voltage V_cc applied to the cathode lines B₁ through B₆₄ is set at 10 V, which is equal to the source voltage of the system.

In FIG. 1, at first the scanning switch 5₁ is switched to 0 V and the cathode line B₁ is scanned. The reverse bias voltage of 10 V is applied to the other cathode lines B₂ through B₆₄ via the scanning switches 5₂ through 5₆₄. Further, the

current sources

2₁ and 2₂ are connected to the anode lines A₁ and A₂ via the driving switches 6₁ and 6₂. Still further, 0 V is applied to the other anode lines A₃ through A₂₅₆ via the shunt switches 7₃ through 7₂₅₆.

Accordingly, FIG. 1 illustrates that only the luminous elements E₁,1 and E₂,1 emit light because only these elements are biased in the forward direction such that driving currents flow into these elements from the

current sources

2₁ and 2₂, as indicated by arrows in the figure. In the state of FIG. 1, the luminous elements indicated by a hatched capacitor are being charged, respectively, in the direction of the polarity shown in the figure. Then, the following reset control is carried out in shifting the scan so that a state of emission in which the luminous elements E₂,2 and E₃,2 emit light, as shown in FIG. 4, is brought about from the state of emission in FIG. 1.

That is, before shifting the scan from the cathode line B₁ in FIG. 1 to the cathode line B₂ in FIG. 4, all of the driving switches 6₁ through 6₆₄ are turned off, and all of the scanning switches 5₁ through 5₆₄ and the shunt switches 7₁ through 7₂₅₆ are switched to 0 V, to shunt all of the anode lines A₁ through A₂₅₆ and the cathode lines B₁ through B₆₄ to 0 V, as shown in FIG. 2. When all are reset to 0 V, all of the anode lines and cathode lines have the same potential of 0 V, so that any electric charge stored or charged in each luminous element is discharged via the routes indicated by arrows in the figure. In this way, the electric charge stored or charged in all of the luminous elements becomes zero instantly. After discharging the electric charge stored in all of the luminous elements to zero as described above, only the scanning switch 5₂, which corresponds to the cathode line B₂, is switched to the side of 0 V to scan the cathode line B₂ as shown in FIG. 3. At the same time, only the driving switches 6₂ and 6₃ are switched to the side of the

current sources

2₂ and 2₃ and the shunt switches 7₁ and 7₄ through 7₂₅₆ are turned on to apply 0 V to the anode lines A₁ and A₄ through A₂₅₆.

When these switches are switched and the cathode line B₂ is scanned, charging currents rush into the luminous elements E₂,2 and E₃,2, which are to emit light next, via a plurality of routes as indicated by arrows in FIG. 3. The electric charges stored in all of the luminous elements are zero, as described above, and thus the parasitic capacitors C of the respective luminous elements are instantly charged.

That is, the charging currents flow into the luminous element E₂,2 via a route of current source 2₂ →driving switch 6₂ →anode line A₂ →luminous element E₂,2 →scanning switch 5₂, as well as via a route of scanning switch 5₁ →cathode line B₁ →luminous element E₂,1 →luminous element E₂,2 →scanning switch 5₂, via a route of scanning switch 5₃ →cathode line B₃ →luminous element E₂,3 →luminous element E₂,2 →scanning switch 5₂, . . . and via a route of scanning switch 5₆₄ →cathode line B₆₄ →luminous element E₂,64 →luminous element E₂,2 →scanning switch 5₂, at the same time. In this way, the luminous element E₂,2 is charged instantly by these plurality of charging currents, and emits light. Then, the state instantly shifts to the stationary state shown in FIG. 4.

Further, the charging currents flow into the luminous element E₃,2 via a route of current source 2₃ →driving switch 6₃ →anode line A₃ →luminous element E₃,2 →scanning switch 5₂, as well as via a route of scanning switch 5₁ →cathode line B₁ →luminous element E₃,1 →luminous element E₃,2 →scanning switch 5₂, via a route of scanning switch 5₃ →cathode line B₃ →luminous element E₃,3 →luminous element E₃,2 →scanning switch 5₂, . . . and via a route of scanning switch 5₆₄ →cathode line B₆₄ →luminous element E₃,64 →luminous element E₃,2 →scanning switch 5₂, at the same time. In this manner, the luminous element E₃,2 is charged instantly by these plurality of charging currents, and emits light. Then, the state shifts to the stationary state shown in FIG. 4 instantly.

As described above, according to the first driving system, all of the cathode lines and anode lines are connected once to 0 V, i.e., the ground potential, to perform a reset before shifting to the next scan. Thus, when the scan is switched to the next scan line, luminous elements on the switched scan line can emit light instantly.

Although the luminous elements other than the luminous elements E₂,2 and E₃,2 are charged via the routes indicated by arrows in FIG. 3, such charging direction is the reverse bias direction, so that there is no possibility that the luminous elements other than the luminous elements E₂,2 and E₃,2 will emit light erroneously. Furthermore, although current sources 2₁ through 2₂₅₆ have been used as the driving sources in the example shown in FIGS. 1 through 4, the same effect may be realized also by using voltage sources instead.

FIGS. 5 through 8 show a second driving system of the present invention.

The second driving system corresponds to a case when all of the cathode lines and anode lines are reset once to the source voltage V_cc =10 V before the next cathode line is scanned. In order to accomplish this resetting method, three-point change-over switches are used as the driving switches 6₁ through 6₂₅₆. In each of these three-point switches, a first contact is opened, a second contact is connected to the current sources 2₁ through 2₂₅₆, and a third contact is connected to the source voltage V_cc =10 V, respectively, in the circuit shown in FIGS. 5 through 8. Because the portions of the circuit structure other than the driving switches 6₁ through 6₂₅₆ are the same as that of the first driving system described above, the explanation of such other portions will not be repeated here.

Operations for emitting light by means of the second driving system will be explained with reference to FIGS. 5 through 8.

The operations described below are with reference to cases when the luminous elements E₁,1 and E₂,1 emit light by scanning the cathode line B₁ and, then, the luminous elements E₂,2 and E₃,2 emit light by shifting the scan to the cathode line B₂ in a manner similar to the first driving system described above.

In FIG. 5, the scanning switch 5₁ first is switched to 0 V and the cathode line B₁ is scanned. The reverse bias voltage of 10 V is applied to the other cathode lines B₂ through B₆₄ via the scanning switches 5₂ through 5₆₄. The

current sources

2₁ and 2₂ are connected to the anode lines A₁ and A₂ via the driving switches 6₁ and 6₂, 0 V is applied to the other anode lines A₃ through A₂₅₆ via the shunt switches 7₃ through 7₂₅₆.

As shown in FIG. 5, only the luminous elements E₁,1 and E₂,1 emit light because only these elements are biased in the forward direction such that driving currents flow into these elements from the

current sources

2₁ and 2₂ as indicated by arrows in the figure. In FIG. 5, the luminous elements indicated by a hatched capacitor are being charged, in the direction of the polarity shown in the figure. Then, a reset control is carried out by shifting the scan so that a state of emission in which the luminous elements E₂,2 and E₃,2 emit light as shown in FIG. 8 is brought about from the state of emission in FIG. 5.

Thus, before shifting the scan from the cathode line B₁ in FIG. 5 to the cathode line B₂ in FIG. 8, all of the shunt switches 7₁ through 7₂₅₆ are turned off, and all of the scanning switches 5₁ through 5₆₄ and the driving switches 6₁ through 6₂₅₆ are switched to 10 V, to shunt all of the anode lines A₁ through A₂₅₆ and the cathode lines B₁ through B₆₄ to 10 V once to reset all by 10 V, as shown in FIG. 6. When all are reset to 10 V, all of the anode lines and cathode lines have the same potential of 10 V, so that electric charge stored or charged in each luminous element is discharged via the routes indicated by arrows in the figure. In this way, the electric charge stored or charged in all of the luminous elements becomes zero instantly.

After discharging the electric charge stored in all of the luminous elements to zero, as described above, only the scanning switch 5₂ which corresponds to the cathode line B₂ is switched to 0 V to scan the cathode line B₂, as shown in FIG. 7. At the same time, the driving switches 6₂ and 6₃ are switched to the side of the

current sources

2₂ and 2₃ and the other driving switches 6₁ and 6₄ through 6₂₅₆ are switched to the open end side. Further, the shunt switches 7₁ and 7₄ through 7₂₅₆ are turned on to apply 0 V to the anode lines A₁ and A₄ through A₂₅₆.

When these switches are switched and the cathode line B₂ is scanned, charging currents rush into the luminous elements E₂,2 and E₃,2, which are to emit light next, via a plurality of routes as indicated by arrows in FIG. 7. The electric charges stored in all of the luminous elements are zero, as described above, and thus the parasitic capacitors C of the respective luminous elements are charged instantly.

That is, the charging currents flow into the luminous element E₂,2 via a route of current source 2₂ →driving switch 6₂ →anode line A₂ →luminous element E₂,2 →scanning switch 5₂, as well as via a route of scanning switch 5₁ →cathode line B₁ →luminous element E₂,1 →luminous element E₂,2 →scanning switch 5₂, via a route of scanning switch 5₃ →cathode line B₃ →luminous element E₂,3 →luminous element E₂,2 →scanning switch 5₂, . . . and via a route of scanning switch 5₆₄ →cathode line B₆₄ →luminous element E₂,64 →luminous element E₂,2 →scanning switch 5₂, at the same time. In this way, the luminous element E₂,2 is charged instantly by these plurality of charging currents, and emits light. Then, the state instantly shifts to the stationary state shown in FIG. 8.

Further, the charging currents flow into the luminous element E₃,2 via a route of current source 2₃ →driving switch 6₃ →anode line A₃ →luminous element E₃,2 →scanning switch 5₂, as well as via a route of scanning switch 5₁ →cathode line B₁ →luminous element E₃,1 →luminous element E₃,2 →scanning switch 5₂, via a route of scanning switch 5₃ →cathode line B₃ →luminous element E₃,3 →luminous element E₃,2 →scanning switch 5₂ . . . and via a route of scanning switch 5₆₄ →cathode line B₆₄ →luminous element E₃,64 →luminous element E₃,2 →scanning switch 5₂, at the same time. In this manner, the luminous element E₃,2 is charged instantly by these plurality of charging currents, and emits light. Then, the state instantly shifts to the stationary state shown in FIG. 8.

As described above, according to the second driving system, all of the cathode lines and anode lines are connected once to 10 V, i.e., the source voltage, to perform a reset before shifting to the next scan, so that when the scan is switched to the next scan line, luminous elements on the switched scan line can emit light instantly.

Although the luminous elements other than the luminous elements E₂,2 and E₃,2 to emit light are charged, respectively, via routes as indicated by arrows in FIG. 7, such charging direction is the reverse bias direction, so that there is no possibility that the other luminous elements will emit erroneously.

Although the current sources 2₁ through 2₂₅₆ have been used as the driving sources in the example shown in FIGS. 5 through 8, the same effect may be realized also by using voltage sources instead.

FIGS. 9 through 12 show a third driving system of the present invention.

The third driving system corresponds to a case when all of the cathode lines B₁ through B₆₄ are reset to 10 V, and the anode lines A₁ through A₂₅₆ are preset, in order to be ready for the next emission before the next cathode line is scanned. Because the circuit structure itself is the same as that of the second driving system described above, explanation of such structure will not be repeated here.

Operations for emitting light by means of the third driving system will be explained with reference to FIGS. 9 through 12.

The operations described below are with reference to cases when the luminous elements E₁,1 and E₂,1 emit light by scanning the cathode line B₁ and then the luminous elements E₂,2 and E₃,2 emit light by shifting the scan to the cathode line B₂ in a manner similar to the first and second driving systems described above.

In FIG. 9, the scanning switch 5₁ is first switched to 0 V and the cathode line B₁ is scanned. The reverse bias voltage of 10 V is applied to the other cathode lines B₂ through B₆₄ via the scanning switches 5₂ through 5₆₄. The

current sources

2₁ and 2₂ are connected to the anode lines A₁ and A₂ via the driving switches 6₁ and ₂, and 0 V is applied to the other anode lines A₃ through A₂₅₆ via the shunt switches 7₃ through 7₂₅₆.

As shown in FIG. 9, only the luminous elements E₁,1 and E₂,1 emit light because only these elements are biased in the forward direction such that driving currents flow into these elements from the

current sources

2₁ and 2₂ as indicated by the arrows in the figure. FIG. 9, the luminous elements indicated by a hatched capacitor are being charged in the direction of the polarity shown in the figure. Then, a reset control is carried out by shifting the scan so that a state of emission in which the luminous elements E₂,2 and E₃,2 emit light as shown in FIG. 12 is brought about from the state of emission in FIG. 9.

Thus, before shifting the scan from the cathode line B₁ in FIG. 9 to the cathode line B₂ in FIG. 12, all of the scanning switches 5₁ through 5₆₄ are switched to 10 V to reset all as shown in FIG. 10. Further, for the anode lines, only the driving switches 6₂ and 6₃, which correspond to the luminous elements E₂,2 and E₂,3 that emit light, are connected to 10 V for preset, and the other driving switches 6₁ and 6₄ through 6₂₅₆ are connected to the open end side. Further, the shunt switches 7₁ and 7₄ through 7₂₅₆ are turned on to achieve connection to 0 V.

When all of the cathode lines B₁ through B₆₄ are reset to 10 V and the anode lines A₂ and A₃ are preset to the source voltage of 10 V, electric charge stored or charged in each luminous element is charged/discharged via the routes indicated by arrows in the figure. In this way, the electric charge stored in each of the luminous elements E₂,1 through E₂,64 and E₃,1 through E₃,64, connected to the anode lines A₂ and A₃, which are to be caused to emit light, becomes zero instantly.

After discharging the electric charge stored in each of the luminous elements E₂,1 through E₂,64 and E₃,1 through E₃,64 to zero as described above, the scanning switch 5₂ is switched to of 0 V to scan the cathode line B₂ as shown in FIG. 11. At the same time, the driving switches 6₂ and 6₃ are switched to the side of the

current sources

2₂ and 2₃.

When these switches are switched and the cathode line B₂ is scanned, charging currents rush into the luminous elements E₂,2 and E₃,2, which are to emit light, via a plurality of routes as indicated by arrows in FIG. 11, thus charging the parasitic capacitor C of the respective luminous elements instantly.

That is, the charging currents flow into the luminous element E₂,2 via a route of current source 2₂ →driving switch 6₂ →anode line A₂ →luminous element E₂,2 →scanning switch 5₂, as well as via a route of scanning switch 5₁ →cathode line B₁ →luminous element E₂,1 →luminous element E₂,2 →scanning switch 5₂, via a route of scanning switch 5₃ →cathode line B₃ →luminous element E₂,3 →luminous element E₂,2 →scanning switch 5₂, . . . and via a route of scanning switch 5₆₄ →cathode line B₆₄ →luminous element E₂,64 →luminous element E₂,2 →scanning switch 5₂, at the same time. In this way, the luminous element E₂,2 is charged instantly by these plurality of charging currents, and emits light. Then, the state shifts to the stationary state shown in FIG. 12 instantly.

Further, the charging currents flow into the luminous element E₃,2 via a route of current source 2₃ →driving switch 6₃ →anode line A₃ →luminous element E₃,2 →scanning switch 5₂, as well as via a route of scanning switch 5₁ →cathode line B₁ →luminous element E₃,1 →luminous element E₃,2 →scanning switch 5₂, via a route of scanning switch 5₃ →cathode line B₃ →luminous element E₃,3 →luminous element E₃,2 →scanning switch 5₂, . . . and via a route of scanning switch 5₆₄ →cathode line B₆₄ →luminous element E₃,64 →luminous element E₃,2 →scanning switch 5₂, at the same time. In this manner, the luminous element E₃,2 is charged instantly by these plurality of charging currents, and emits light. Then, the state shifts to the stationary state shown in FIG. 12 instantly.

As described above, according to the third driving system, all of the cathode lines are reset to 10 V and the anode lines are preset to be ready for the next emission before shifting to the next scan, so that when the scan is switched to the next scan line, luminous elements on the switched scan line can emit light instantly.

Although the luminous elements other than the luminous elements E₂,2 and E₃,2 are charged via routes as indicated by arrows in FIG. 11, such charging direction is the reverse bias direction, so that there is no possibility that luminous elements other than the luminous elements E₂,2 and E₃,2 will emit light erroneously.

Although all of the cathode lines have been reset to 10 V in the third driving system described above, all of the cathode lines may instead be reset to 0 V. Further, although current sources 2₁ through 2₂₅₆ have been used as the driving sources in the example shown in FIGS. 9 through 12, the same effect may be realized by using voltage sources instead.

As is apparent with reference to each figure of FIGS. 3, 7 and 10 described above, the luminous elements E₂,2 and E₃,2 are charged not only from the

current sources

2₂ and 2₃, but also from the other luminous elements connected to the anode lines A₂ and A₃ at the same time via the cathode lines B₁ and B₃ through B₆₄ to which the reverse bias voltage is applied.

Therefore, when a large number of luminous elements are connected to the anode lines, the luminous elements E₂,2 and E₃,2 may emit light just by the charging current obtained via those other luminous elements, if for a short time. Accordingly, the current sources 2₁ through 2₂₅₆ of the anode line driving circuit 2 may be obviated by scanning the cathode lines with a period shorter than a duration of the emission caused by the charging current obtained via the other luminous elements.

Further, although the embodiments described above have been explained in connection with examples exemplifying the system of scanning cathode lines and driving anode lines, the same invention may be realized by scanning anode lines and driving cathode lines.

As described above, according to the present invention, the parasitic capacitors of luminous elements to emit light are charged by the driving sources via the drive lines and also by the reverse bias voltage of the scan lines at the same time via the parasitic capacitors of the other luminous elements not emitting. This is accomplished by switching the scanning position to the next scan line after resetting all of the scan lines, so that an end-to-end voltage of the luminous elements to emit light may be built up instantly to a voltage which allows the emission, thus allowing the luminous elements to emit light instantly. Further, because the charge obtained via the other luminous elements is utilized, the capacity of each driving source may be reduced and the driving unit can be miniaturized.

Moreover, the driving unit is adapted to be able to emit light quickly while eliminating all of the driving sources on the drive line side, so that the driving unit may be further simplified and miniaturized.

It will be apparent to those skilled in the art that various modifications and variations can be made in the driving system of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A driving system for driving luminous elements, the driving system comprising:

a plurality of intersecting anode and cathode lines arranged in a matrix, the anode lines being one of scan lines and drive lines, and the cathode lines being one of other of scan lines and drive lines;

a plurality of luminous elements, each of the luminous elements being coupled to one of the scan lines and one of the drive lines at a point where the scan and drive lines intersect, and

control circuitry for causing at least one of the luminous elements to emit light by executing scanning of at least one of the scan lines and, during a predetermined period of the scanning, by coupling a driving source to at least one of the drive lines in synchronism with the scanning, the control circuitry resetting the scan lines before switching to a subsequent scan line by coupling each of the scan lines to a same reset voltage potential.

2. The driving system for driving luminous elements according to claim 1, wherein the reset voltage potential is a ground potential.

3. The driving system for driving luminous elements according to claim 1, wherein the reset voltage potential is a supply potential.

4. The driving system for driving luminous elements according to claim 1, wherein the resetting function performed by the control circuitry is performed without use of any drive line drive source.

5. The driving system for driving luminous elements according to claim 2, wherein the resetting function performed by the control circuitry is performed without use of any drive line drive source.

6. The driving system for driving luminous elements according to claim 3, wherein the resetting function performed by the control circuitry is performed without use of any drive line drive source.

7. The driving system for driving luminous elements according to claim 1, wherein the control circuitry resets all of the scan lines before switching to each subsequent scan line by simultaneously coupling each of the scan lines to the same reset voltage potential.

8. The driving system for driving luminous elements according to claim 1, wherein the luminous elements are organic electroluminescense elements.

9. The driving system for driving luminous elements according to claim 1, wherein the control circuitry comprises a line scanning circuit for scanning the scan lines, and a line driving circuit for driving the drive lines.

10. The driving system for driving luminous elements according to claim 7, wherein the line driving circuit comprises a plurality of current sources each for driving a different one of the drive lines.

11. The driving system for driving luminous elements according to claim 7, wherein the line driving circuit comprises a plurality of voltage sources each for driving a different one of the drive lines.

12. The driving system for driving luminous elements according to claim 7, wherein the line scanning circuit applies a ground potential to each scan line being scanned and a reverse bias voltage to each scanning line not being scanned.

13. The driving system for driving luminous elements according to claim 7, further comprising a drive line resetting circuit including shunt switches for resetting the drive lines to a ground potential.

14. A method of driving luminous elements in a driving system comprising a plurality of intersecting anode and cathode lines arranged in a matrix, the anode lines being one of scan lines and drive lines, and the cathode lines being one of other of scan lines and drive lines; a plurality of luminous elements, each of the luminous elements being coupled to one of the scan lines and one of the drive lines at a point where the scan and drive lines intersect; and control circuitry for causing at least one of the luminous elements to emit light; the method comprising the steps, performed using the control circuitry, of:

scanning at least one of the scan lines;

driving at least one of the drive lines in synchronism with the scanning; and

resetting the scan lines before switching to a subsequent scan line by coupling each of the scan lines to a same reset voltage potential.

15. The method according to claim 12, wherein the resetting step comprises:

simultaneously coupling each of the scan lines to the same reset voltage potential.

16. The method according to claim 12, wherein the resetting step comprises:

coupling all of the scan lines to a same ground potential;

turning off all drive sources coupled to one end of the drive lines; and

shunting the other end of the drive lines to a same ground potential.

17. The method according to claim 12, wherein the resetting step comprises:

coupling all of the scan lines to a same source potential;

coupling one end of each of the drive lines to a same source potential; and

shunting the other end of the drive lines to a same ground potential.

18. The method according to claim 12, wherein the resetting step comprises:

coupling all of the scan lines to a same source potential;

turning off only selected ones of drive sources coupled to one end of the drive lines; and

shunting the other end of the drive lines to a same ground potential.